Peter's death happened as he parked up his UK plated Audi outside his luxury villa on the Costa Del Sol, near Fuengirola in Spain, as he returned home from the Gym.
The Salford born father of two children known as Snaggle to his friends and family, is said to have died instantly after one of the seven bullets fired at him struck his heart.
Peter was gunned down in a residential street called Calle Ofrebres, which sits in the hills which run alongside the Costa del Sol, at around 3.15pm on Thursday afternoon.
It is thought that another vehicle pulled alongside him, whereupon shots were fired before the vehicle sped off from the scene.
Emergency services made a desperate attempt to save his life at the scene by practising CPR but sadly they were unable to save him.
Officers have so far made no arrests and although no official comment has been made by police, a Spanish newspaper is reporting that they are focusing on the theory that the ex-pat was murdered in a drugs-related incident, after Williamson had been arrested earlier in the year (March) suspected of trafficking cannabis resin via a transport firm from Malaga to an unconfirmed destination.
Although it should be made clear that there is no evidence we have seen to support the papers claims as no charges were made against Williamson and it is thought that his arrest was a case of mistaken identity on behalf of the Spanish police.
Regardless it is a devastating loss to his family, especially so to his two children who will now grow up without a father, we offer his family and friends our condolences at this time and hope that those responsible for his barbaric murder are swiftly brought to justice.